Results of the Lake Minnetonka Underwater Archaeology Project: Anomaly Identification and Anomaly Assessment (LMNA-10)

Minnesota Archaeology Licenses  20-012, 20-013, 21-048, 21-191

Research Design

A goal of the LMNA-10 Project - in addition to identifying previously recorded anomalies on the lake bottom - was to conduct targeted side and down imaging sonar survey in shallow areas of the lake prior to seasonal vegetation growth. Re-investigating shallow areas using remote sensing - under conditions that differed from the original survey - has produced significant results. Without thick weeds to block the sonar beam from extending to the lake bottom or obscuring submerged cultural resources, MHM has been identifying a significant number of wrecks and sites in the shallow water. Additionally, MHM has been also re-surveying deeper sections of Lake Minnetonka using newer and improved sonar equipment as time allows. MHM determined which anomalies would be investigated from an analysis of sonar data recorded between 2011-2021. Each anomaly was assigned a number upon its recognition as a possible site.

The 37 anomalies examined using SCUBA during the LMNA-10 Project were A698, A741, A800, A807, A836, A854, A855, A856, A860, A862, A864, A869, A884, A885, A890, A892, A897, A898, A907, A908, A910, A916, A1000, A1010, A1022, A1023, A1024, A1026, A1035, A1037, A1038, A1039, A1052, A1053, A1056, A1057, and A1058. Additionally, MHM re-visited the Wooden Inboard Motor Boat Wreck site (21-HE-564, Anomaly 26.1), the Owens Cruiser Deluxe Wreck site (21-HE-565, Anomaly 55), and the Larson Game Warden Wreck (Anomaly 726) to answer archaeological questions. Using data accumulated from the fieldwork as a starting point, MHM conducted research to place newly recognized nautical archaeological sites and anomalies into their historical contexts. Minnesota Archaeological Site Forms were filed with the OSA when appropriate.

Methodology

The methodology used to identify and rudimentarily document underwater archaeological anomalies is straightforward. MHM used the GPS coordinates of a wreck or an anomaly - taken from the data imbedded in the sonar data - to drop a weighted diver down buoy near the target. The dive boat anchored a short distance away from the buoy and divers geared up for the dive. At any given time, there were between two and four divers underwater. If the buoy anchor weight landed near and sometimes on the anomaly or wreck, no search for the target was conducted. However, for a variety of reasons, a brief search for the target was conducted until it was located or it was determined that the anomaly was a false sonar return. If a cultural or natural resource was located, the divers photographed and recorded video of the site or object, logged its basic measurements, examined any obvious attributes, and measured sediment build-up (if appropriate).

Results

After the completion of the LMNA-10 Project fieldwork in September 2021, there are now 94 identified wrecks on the bottom of Lake Minnetonka or that were once on the bottom, including a Woodland Culture dugout canoe removed from the lake in 1934. Of these wrecks, 62 of them have 61 Minnesota archaeological site numbers; 2 wrecks are features of one site. Further, 4 other types of maritime sites have archaeological site numbers and there are 39 maritime sites or objects without numbers. Additionally, 53 'other' objects have been identified that do not have site numbers, among them 13 vehicles that include 4 snowmobiles, 2 trucks, and 7 cars. During the LMNA-10 Project specifically – of the 37 unknown anomalies and 3 known wrecks investigated – MHM and its volunteers accumulated important data about the wrecks and confirmed the existence of 11 new wrecks, 4 new submerged maritime sites (2 of which are associated with other known archaeological sites), 3 ‘other’ objects, and 19 natural objects or false sonar returns.

In Copyright. This work is copyrighted to Ann Merriman, Christopher Olson, and Maritime Heritage Minnesota. It cannot be duplicated, altered, or hosted online by an unauthorized third party. It cannot be sold for a profit or used to make a profit by any unauthorized third party and no commercial use is allowed. It can be used as a scholarly resource with proper citation to Ann Merriman, Christopher Olson, and Maritime Heritage Minnesota.

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